Dredge



W. W. JOHNSON DREDGE July 30, 1940.

Filed June 1, 1938 3 Sheets-Sheet 1 i fl? INVENTOR WALTER W JO NSON m H/5 ATTORNEY July 30, 1940.

w. w. JOHNSON DREDGE 3 Sheets-Sheet 2 Filed June 1, 1938 INVENTOR J/O/NSON H/5 ATTORNEY Jilly 30, 1940.

w. w, JOHNSON DREDCTE Filed June 1. 1938 3 Sheets-Sheet 3 JJlE INVENTOR WQLTEE WJ'O NSON Wt 54 H ATTORNEY Patented July 30, 1940 U ITED STATES: PATENT OFFICE Walter W. Johnson Company, San Califl, acorporation of Nevada Francisco,

, Application June 1, 1938, Serial No. 211,198

. v 6 Claims.

- My invention relates to'ladder dredges, such as. employed ingold dredging, and the broad object of. the invention is to provide; means for handling large boulderscarried up the ladder so that. the boulders'may be removed simply and y. l s The invention possesses other objects and features of advantage, some of which, with the foregoing, will be set forth in the following description of my invention. It is to be understood that I do not limit myself to this disclosure of species of my invention,,as I may adopt variant embodiments thereof within. the scope of the claims.

Referring to the drawings: c Figure 1- is a vertical sectional view taken through the hopperof a dredge embodying my invention, portions of the hopper wall being broken away, to show the boulder dump mecha- ;and V Figure 2 is a vertical sectional view of the same taken in a plane indicated by line 2- 2 of Figure 1, showing the boulder discharge chuteand the door in the side wall of the hopper through which the boulders are dumped. v,

Figure 3 is a vertical sectional-yiewsimilar to Figure 2, and showing a modified form of construction; and v Figure 4 is a vertical sectional view of the same taken in a plane indicated by line 4-4 ofFigure 3. In ladder dredges, such as those employed in gold dredging, it frequently happensthat a large boulder weighing perhaps a ton or more, is picked up by a bucket. Theusual practice has been to stop the ladder and remove the boulder by block 35 and tackle. This is an arduous and time taking operation. By the mechanism of the present invention these boulders are easily handled and dumped into a special discharge chute provided for that purpose, and this maybe done without 40 stopping the ladder. I

In terms of broad inclusion, the improved dredge comprises a ladder for elevating material and dropping it into a hopper, and a dump mechanism for deflecting a boulder from its nor- 45 mal path and discharging it into a. special chute alongside the hopper.

In greater detail, and referring to Figures 1 and 2 of the drawings, a gold dredge embodying the invention comprises the usual ladder having 50 buckets 2 linked together and running over an upper drive tumbler 3. The material carried up by the ladder buckets is dumped into a suitable hopper 4 having a chute 6 at the bottom for directing the material into a revolving screen 1.

55 This is all standard construction in gold dredges of this type, and it is understood that the structural details may vary within wide limits.

If a large boulder is picked up by a bucket it is ordinarily removed before'reaching the top of the ladder to prevent its being dumped into the hop- 5 per and fouling the mechanism. The buckets travel relatively slowly, and the customary practice has been that when the operator sees a boulderbeing elevated he stops the ladder. A crew of men was then required to rig up'block and tackle to remove the boulder.

All this is avoided in the improved dredge of the present invention by a boulder dump mechanism mounted adjacent the upper end of the ladder. A boulder discharge opening 8 is provided in the side wall of hopper 4 opposite the ladder andbelow the point Where the buckets start discharging the elevated material into the hopper. A sliding door 9' is provided for normally closing this opening, and may be raised by an air cylinder ll suspended from the superstructure of the dredge and having a duct I2 leading to the control cabin where the operator may open and close the door at will by manipu-' lating a suitable valve.

Outside the opening 8 a chute I3 is arranged to receive the boulders and convey the same out over the edge of the dredge. The wall of the chute opposite the opening is suitably reinforced to withstand the shock of boulders being thrown out, and the bottom of the chute is likewise reinforced as by rails l4.

Means are provided for deflecting a boulder from its path of fall and dumping it into chute l3. For this purpose a dump shelf or grid I6 is pivotally mounted adjacent the lower edge of opening 8 for movement from a boulder receiving position projecting horizontally into the hop per to a discharge position standing vertically outside the opening. The latter position is shown by dotted lines in Figure 1. In the receiving position the shelf extends across the path of falling material, and the open grid structure permits all but the large boulders to fall through. In normal operation of the dredge the shelf stands outside the opening with the door closed behind it; the door being opened and the dump shelf lowered only when the operator sees a boulder being elevated.

A counterweight I1 is provided for balancing the grid, and an air cylinder I8 is also connected to a lever on the shelf mounting shaft IQ for swinging the shelf from one position to another. Ducts 2| for admitting air into opposite ends of the cylinder lead to the control cabin where the 2 i operator may swing the dump shelf in or out at will by manipulating suitable valves. After the operator feels the jar of a boulder landing on the shelf he swings the latter out to dump the boulder into chute l3. Door 9 is then closed and the dredge operates as usual until another boulder is picked up.

Since the laddertravels relatively slowly, and since thedump shelf .16 is positioned fairly well below the point where the boulder drops out of its bucket, a watchful operator can swing the shelf up to discharge the boulder without stopping the ladder. If desiredhowevertheladdermay" be stopped momentarily until the boulder h been dumped.

rastenou'g h,;or if the ladder has not-been'st'oppedf. To preventjamming the mechanism in thisev ent safetymeans are provided for-allowing the shelf to be depressed- For this purpose th'e lower end of cylinder W I 8 is pivotally supported 'onfan' am 221 having one end jmo unt'ed on a pin 23 and the other end workin'gf'in a guide 'slot 24. Arm 2 Z-"i's supported by a bar 26 connected-with"ai-rocker arm 21 having heavy counterbalance -28 suspended fromthe other endt 1 By this arrangement the actuating 1 cylinder i 8 m y. be depressed" bodily to permit downward yielding of 'the shelf, lshouldfl the force bearing down; on the latter be sufficient to overcome the holding-force of weight '38. The latter is-"of course'- heavy enoughfand "the "mechanical adi ama 's de n dl hei he fl d w l go wnili er heiqrdina y;i fi sf S portanddischarge aboulder.

Figures 3 and 4-illustratea modified construction-'inwhich a dump shelf or grid 29 is supported in operative position by a 'pair of side chains. Each chain 3|, is suspended from a fixed element of the frame by a rod 32 held up by a heavy compression spring 33 totake up shock.- The flexibility of the chains permits them to fold so as to be out of the way for closing the door. The dump shelf is moved by an air cylinder 34 having its lower end supported directly on a girderof the dredge; there being no means allowing the unit to depress in this case because the arrangement of the shelf at a higher point than in Figure 1 makes jamming highly improbable and a safety feature unnecessary.

A variant arrangement of door cylinder 35 is also shown to eliminate the suspended cylinder shown in Figure 2. The boulder discharge chute is also somewhat different in that an arrangement of blocks 31 is provided under the head end to take up the shock of outcoming boulders.

Another feature shown in Figure 3 is a gate 38 for holding the boulders from immediately rolling completely down the chute. Such a gate is desirable to hold back the boulders so that they can all be dumped at one point instead of strewn about the bottom of the area being dredged. The gate 38 is preferably in the form of a grid pivoted at its upper end and held down in the chute by a pair of elbow arms 39. The elbow pin is slightly below center-when the arms are'extended to keep them'from knifing up and a strap 4| across the top holds them from buckling .down. A rope 42 connecting the elbow pin with "lever 43 permits an operator to break the arms and allow the gate to swing up to free the collected bouldersv A counterweight 44 keeps the gate up, v and. alever 46 provides means for an operator The buckets clear the end of the shelf so that N there is no danger of a bucket catching on it, d but a large boulder on the shelf mightpro ject-out far enough to catch the down coming edge of a j bucket if the boulder has notbeen thrown out to w r the a e-.11;

Iclaini: H l

1 A dredge comprising a ladder for elevating material,,a pivotally mounted dump shelf extending across the pathof material dropped from the ladder "forcatching *a boulder, means for swinging thesh'elf upwardly to discharge the bouldery and -means for yieldably supporting the 'shelf'in'its extended po'sition.'--

2'. Acreagecompnsm a ladder for elevating material, a pivotally mounted dump shelf extendingacross the-path of material dropped from the ladder-for catching a boulder, means for swinging -the' shelf upwardly: to discharge the boulder',{ and counterbalance 'me a'ns' 'for' yieldably 3 theladder forcatchinga boul'der, a pressure fluid cylinder operably connected toi'swing the shelf upward-1y for discharging the boulder, and means for yieldably supporting-the cylinder; 5 i.

4. A dredge comprising a ladder forfelevating' material, a 'pivotally mounted dum'p shelf. extending across the path of material dropped from the ladder forcatching a boulder, a fixed element above the shelf, flexible means for suspending the free end of the shelf from said fixed element, and. meansfor swinging the shelf upwardly to. discharge the boulder. I

5. A dredge comprising a ladder for elevating material, a dump shelf extending across the path of material dropped from the ladder for catching a boulder, means for moving the shelf to discharge the bouldr, and means for yieldably supporting the shelf in its extended position.

6. A dredge comprising a ladder for elevating material, a hopper into which the material from the ladder is dropped and having an opening in the side thereof, a dump shelf extending into the hopper for catching a boulder, means for yieldably supporting the shelf in extended position, means for moving the shelf to discharge the boulder through said opening, and a door for closing the opening.

WALTER W. JOHNSON. 

